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Test 2 Review
Chapter 7, 8,
51
Geology
Undergraduate 1
10/22/2012

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Term
Detrital Sedimentary Rocks
Definition
 Nonorganic, solid particles put through both mechanical and chemical weathering. Clay minerals and quartz are the chief constituents of most detrital rocks. 85% of all sedimentary rocks. chemical resistant. Composed of minerals with slow rates of chemical weathering, or the products of chemical weathering. Composition varies with weathering intensity or length of transport.
Term
Chemical Sedimentary Rocks
Definition
When ions in solution are precipitated by either inorganic or biological processes, the material is known as chemical sediment, and it makes these rocks.
Term
Organic Sedimentary Rocks
Definition
Coal is a prime example; when carbonic plant matter is cemented left over from swamps.
Term
Clasts
Definition
variety of minerals and rock fragments.
Term
What do sediments do?
Definition
Store solar energy and provide a look into the past.
Term
Depositional Environments
Definition
from Glaciers, rivers, dunes are created from wind, shores, both from ocean and river
Term
Lithification
Definition
making sedimentary rocks through compaction and cementation
Term
Common cementation elements
Definition
  • silica (SiO3)
  • calcium carbonate (CaCO3)
  • iron oxide (Fe2O3-H2O)
Term
Compaction relative to clay
Definition
Clays may be compact up to 40%
Term
Diagenesis
Definition
all low-temperature chemical changes that happen under the surface
Term
Inorganc Chemical Rocks
Definition
evaporates
Term
Types of Sandstone?
Definition
  • Quartz sandstone-mostly quartz
  • arkose sandstone- angular grains, feldspars and rock fragments
  • graywacke-dirty sandstone, has quartz, feldspar, clays
Term
Difference between breccia and conglomerate?
Definition
conglomerate uses rounded grain, breccia-angular
Term
Siltstone, mudstone, shale
Definition
  • Siltstone-mostly silt
  • Mudstone- silt and clay, not shale-like layers
  • Shale- red means oxygen present
Term
Precipitation sequence from seawater:
Definition
1) Calcite (CaCO3)
2) Gypsum (CaSO4·2H2O)
3) Halite (NaCl)
Term
Chemical Sedimentary Rocks
Definition

Biochemical sedimentary rocks = biogenic
precipitates
» biogenic = originates from life

Limestone - mostly calcite; often composed
of biogenic grains which may recrystallize
» Typically deposited where there is little or no
clastic sediment
» Can vary from of fossil-free to fossiliferous

Term
Cementation differences between chemical rocks
Definition
coquina-badly cemented, chalk is good
Term
Stromatolite
Definition

–Formed by trapping of sediment by algae
         *Evidence for shallow water
–Some of the earliest fossils

Term
Reefs
Definition
- biogenic buildup; carbonate secreting organisms; marine
–Evidence for shallow water
Term
Chert
Definition

SiO2, micro- or cryptocrystalline
»Remains of silica-secreting microorganisms living in ocean (diatoms, radiolaria)
»Also forms from silica precipitation in pores after burial

Term
Types of Ripples
Definition

asymmetrical-waves go 1 way

oscillatory-goes both ways

Term
Graded bedding -
Definition
grain size decreases upward
»Caused by slowing of current
Term
Trace Fossils
Definition
burrows, footprints, root traces
Term
Metamorphic rocks form
Definition
major parts of shields and mountain belts
Term
metamorphism?
Definition
Process whereby preexisting rock undergoes pronounced changes in texture and mineralogy at T > 200-300ºC while in the solid state
Term
agents of metamorphism
Definition
heat, pressure, chemically active fluids, heat gets greater as you go down
Term
heat effects
Definition
Increased ductility
– Change in mineral
assemblage
Term
pressure (stress)
Definition
Confining pressure - felt
equally in all directions
» Differential stress - added
pressure from tectonic activity
(tension, compression, shear)
Term
pressure effects
Definition
Favors minerals with
dense, compact crystal
structures
» Minerals grow
perpendicular to
maximum pressure
– Produces a parallel
arrangement of platy
minerals called
foliation
– Gives rock layered or
banded appearance
Term
rising magma bodies
Definition
shallow crustal rocks are metamorphosed by increasing T.
Term
subduction
Definition
sediments are metamorphosed by increasing P and T
Term
deep burial
Definition
sedimentary strata are meta-morphosed by moderately increasing P and T
Term
chemically active fluids
Definition
Hydrothermal fluids (hot water); important for ion transport
Term
foliation
Definition
»Rock or slaty cleavage - parallel alignment of microscopic platy minerals
»Schistosity - parallel alignment of visible platy minerals
Term
Gneissic
Definition
banded; layers of light and dark minerals
Term
more textures
Definition
Lineation - parallel alignment of needle-like grains
Porphyroblastic - larger crystals (porphyroblasts) in a finer matrix
Term
protolith
Definition
Parent rock
Term
fluids
Definition
Supplies ions/atoms; can alter composition inherited from protolith
Term
slate
Definition
very fine grained, clay rich
»Slaty cleavage
»Bedding often present
»Metamorphic grade: low
Term
phyllite
Definition
Cleavage surface has sheen
»Mica and/or chlorite grains
Figure 8.14
AN07_004.
Term
schist
Definition
50% visible platy minerals; may have layers or qtz and/or feldspar
»Bedding rare
»Grade: medium to high
»Rock name based on predominant mineral
–Ex: muscovite schist (clay
Term
marble
Definition
Fine to coarsely crystalline calcite
»Parent: limestone or dolomite
Term
quartzite
Definition
Metamorphosed qtz sandstone; almost all qtz
Term
metaconglomerate
Definition
Metamorphosed conglomerate - breaks through pebbles
Term
blueschist
Definition
»Contains glaucophane (amphibole)
»High pressure, relatively low temperature
Term
eclogite
Definition
pyx, garnet; high P, moderate T
Term
three types of metamorphism
Definition
»Contact - associated with plutonism; small scale
»Cataclastic - occurs within fault; very small scale
»Regional - associated with mountain-building; large scale
Term
Aureole
Definition
zone of metamorphosed rock around pluton; non-foliated
Term
skarn
Definition
unique rock formed from metamorphism of protolith of silicate and carbonate (limestone or dolomite) rocks
Term
fault breccia
Definition
broken and crushed rock in fault
Term
mylonite
Definition
hard, fine-grained rock formed from grinding within fault
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